I've read a great many procedures for creating secure passwords, and I've devised a few of my own. Lots of systems exist that purport to offer an easy-to-learn mechanism for creating passwords that would be difficult for a human (or even a computer) to guess, are long enough and complex enough to defeat most brute-force attacks, and yet are memorable. Although I provide a few examples ahead, the important thing to remember is that there's no single right way to create passwords. As long as you avoid making the mistakes that can compromise a password's security, the specifics of how you devise and remember passwords are entirely up to you.
So, what are the most common password mistakes? Whatever else you do, always avoid using the following, in any form, as a password — even in low-security applications:
Names — your own or those of friends, family, pets, or places
Dates of significant events (birthdays, anniversaries, and the like)
Words and phrases someone might associate with you, such as your favorite color, food, or song
Repeated characters, such as gggggg
Easily typed patterns, such as mnbvcx
Common passwords, such as password, password1, and 123456